How to add golden line to my maps?
Math nodes on object's coordinates
There are several approach you can take, the easiest is to build a shader that is capable of recognizing the isolines (lines that have something in common, the same Z in this case).
Start by adding a texture coordinate node. We'll use the object coordinate (the position of it's origin in this case) as a starting point.
Whit a separate XYZ node we isolate the Z channel:

Then we use the math &quot;modulo&quot; node to subdivide the Z channel in several segments, and the math &quot;compare&quot; node to extract an interval from each segment (you can use a color ramp if you want a smooth edge).

We basically obtained the lines, now we just need to use the results as mask for the mix shader node between our two shaders.